Mammograms may detect some cancers that would have otherwise regressed

Nov 24, 2008

Breast cancer rates increased significantly in four Norwegian counties after women there began undergoing mammography every two years, according to a report in the November 24 issue of Archives of Internal Medicine. Rates among regularly screened women remained higher than rates among women of the same age who were screened only once after six years, suggesting that some of the cancers detected by mammography may have spontaneously regressed had they not been discovered and treated.

Throughout Europe, the start of screening mammography programs has been associated with increased incidence of breast cancer, according to background information in the article. "If all of these newly detected cancers were destined to progress and become clinically evident as women age, a fall in incidence among older women should soon follow," the authors write. "The fact that this decrease is not evident raises the question: What is the natural history of these additional screen-detected cancers?"

Per-Henrik Zahl, M.D., Ph.D., of the Norwegian Institute of Public Health, Oslo, and colleagues examined breast cancer rates among 119,472 women age 50 to 64 who were all invited to participate in three rounds of screening mammograms between 1996 and 2001 as part of the Norwegian Breast Cancer Screening Program. They compared these to rates among a control group of 109,784 women age 50 to 64 in 1992, who would have been invited for screening if the program had existed at that time. Cancers were tracked for six years using a national registry, and at the end of that time all participants were invited to undergo a one-time screening to assess breast cancer prevalence.

As anticipated, breast cancer rates were higher among screened women than among the control group before the final prevalence screening. "Even after prevalence screening in controls, however, the cumulative incidence of invasive breast cancer remained 22 percent higher in the screened group," the authors write. Of every 100,000 screened women, 1,909 had breast cancer during the six-year period, compared with 1,564 of every 100,000 in the control group. Screened women were more likely to have breast cancer at every age.

"Because the cumulative incidence among controls never reached that of the screened group, it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of six years," the authors write. "This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress."

"Although many clinicians may be skeptical of the idea, the excess incidence associated with repeated mammography demands that spontaneous regression be considered carefully," they continue. "Spontaneous regression of invasive breast cancer has been reported, with a recent literature review identifying 32 reported cases. This is a relatively small number given such a common disease. However, as some observers have pointed out, the fact that documented observations are rare does not mean that regression rarely occurs. It may instead reflect the fact that these cancers are rarely allowed to follow their natural course."

The findings do not answer the question of whether mammograms prevent deaths from breast cancer, the authors note. "Instead, our findings simply provide new insight on what is arguably the major harm associated with mammographic screening, namely, the detection and treatment of cancers that would otherwise regress," they conclude.

Citation: Arch Intern Med. 2008;168[21]:2311-2316.

Source: JAMA and Archives Journals

Explore further: Chronic inflammation linked to 'high-grade' prostate cancer

add to favorites email to friend print save as pdf

Related Stories

First look at breast microbiota raises tantalizing questions

Mar 24, 2014

The female breast contains a unique population of microbes relative to the rest of the body, according to the first-ever study of the breast microbiome. That study sought to lay the groundwork for understanding how this bacterial ...

Recommended for you

Unraveling the 'black ribbon' around lung cancer

19 hours ago

It's not uncommon these days to find a colored ribbon representing a disease. A pink ribbon is well known to signify breast cancer. But what color ribbon does one think of with lung cancer?

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

E_L_Earnhardt
not rated yet Nov 25, 2008
"Detect" or CAUSE. X-rays CAUSE cancer!
marky
not rated yet Nov 25, 2008
Ionising radiation has been identified as being cancer causing for decades!

Why do we persist in bombarding the body with x-rays every 2 years?

More news stories

Leeches help save woman's ear after pit bull mauling

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Venture investments jump to $9.5B in 1Q

Funding for U.S. startup companies soared 57 percent in the first quarter to a level not seen since 2001, as venture capitalists piled more money into an increasing number of deals, according to a report due out Friday.